class Parent{
    arg1="parent属性";
    private arg2="parent私有属性";
    printParent(){
        console.log("parent方法");
    }

};
class Child extends Parent{
    arg3="child属性";
    printChild(){
        console.log("child方法");
    }
};
class A extends Child{

}
var c1:Child=new Child();
c1.arg1;
c1.printParent();
c1.arg3;
c1.printChild();
var a=new A();


